Follow-up mechanism



Jan. 17, 1950 1. w. DRAKE v2,495,161?.

FOLLOW-UP MECHANISM Filed June 20, 1946 Patented Jan. 17, 1950 FLLOW-UP MECHANISM J ames W. Drake, Rockford, Ill., assignor to Woodward Governor Company, Rockford, Ill., a corporation of Illinois Application .nine zo, 194s, serial No. 618,011

9 claims. (ci. sis-32) This invention relates to mechanism of the type in which a power actuator for an element to be operated is started in response to the movement of a control element and continued in operation until the driven element has been moved to a position corresponding to the new position of the control element.

One object is to provide a mechanism of the above character having a novel follow-up cam which increases the range of operation of the y control element and which permits the use of a control switchY and a stationary contact. Another object is to provide such a mechanism in which the follow-up action is produced by the coaction of two cams, one movable with the control element and the other in unison with the power driven element.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a fragmentary perspective view of part of a follow-up mechanism embodying the novel features of the present invention.

Fig. 2 is a fragmentary section taken substantially along the line 2--2 of Fig. 1.

Fig. 3 is a detailed view of the cam and follower parts.

Fig. 4 is a schematic view and wiring diagram.

In the drawings, the invention is shown for purposes of illustration embodied in an electrical servo actuator for positioning a driven element lsuch as a shaft 5 accurately in accordance with changes in the position of a control element which may be a shaft 6 adapted to be turned to selected positions by manual adjustment of a hand lever 1. The latter may be connected to the shaft through pulleys and a cable 6a.

The servo actuator is a reversible electric motor 8 whose armature 9 is geared to the shaft 5 and turns in opposite directions in response to the energization of windings l and II respectively. Such energization is effected through relays I2 and I3 which are energized by selective closure of two switches I4 and I5 having a common contact 23 movable between stationary contacts I6 and I1, the motor being idle when the contact 23 is in neutral position out of engagement with both stationary contacts, which constitute stops for limiting the movement of the contact 23.

The motor 8 is started in the proper direction in response to readjustment of the hand lever 1 and is stopped after the driven shaft has been turned through a corresponding distance 4which may be a multiple of the movement of the control shaft 6. In accordance with the present invention, such follow-up action is effected by two cams I8 and I8, acting on a follower20 connected to the control device or switches Il, I5, the respective cams being moved in unison with the driven shaft 5 and the control shaft 6. Herein. the cam I9 is fast on the hub of a gear 25, loose on a shaft 2l, which is journaled in a suitable frame 22 that supports the motor 8 and the other rotary parts. The pinion 25 meshes with a gear 24 on the control shaft 6 so that the cam IB turns in unison with the latter. The cam i8 is fast on the shaft 2I and is driven in unison with the driven shaft 5 through speed decreasing gearing 26.

The cams I8 and I9, which are thus adapted for rotation relative to each other about a common axis, are in the present instance of the open face type having peripheral surfaces 21 and 28 which rise gradually and preferably are of similar shape. Herein these surfaces cross each other so as to form a V-shaped notch in which the rollers 29 on the follower 20 are disposed. The follower comprises an arm pivotally connected to the free end of an arm 30 which is swingable about a pivot 3l xed on the frame 22. A cross arm 32 rigid with the arm 30 carries the common switch contact 23 which is thus supported for movement back and forth between the stationary contacts. A contractual spring 33 stretched between the arms 20 and 30 completes the connection between the follower and the common switch contact which connection is adapted to yield and permit movement of the follower arm after the switch contact has reached a limit position against one of the stationary contacts.

When the follower rollers 29 are engaging corresponding points on the engagement surfaces 21 and 28, as shown in full in Fig. 3, the contact 23 will be held in the neutral position and both motor windings I0 and I I will remain deenergized. Now, if by repositioning the control shaft 6, the cam ISI is turned counterclockwise as viewed in Fig. 1, the follower 2U will be raised as shown in phantom in Fig. 3 thereby swinging the contact 23 to close the switch I5. The spring 33 yields to permit continued raising of the follower arm after the contact 23 engages the stop I1. Thereupon the motor 8 will be started in a direction tov turn the cam I8 clockwise until the rise 21 becomes effective to move the contact back to neutral position thereby stopping the motor. When this occurs, the shaft 5 will have been moved through a distance corresponding precise- 3 ly to the rcadjusted position of the hand lever 1.

In a similar way, clockwise readjustment of the control cam I allows a lowering of the follower 2l and closure of the other switch I 4 to start the motor for turning of the shaft 5 in the reverse direction, this being accompanied by counterclockwise turning of the cam I8. Such operation is terminated when the point on the cam surface 21 corresponding to the point on the cam surface 2l then engaging the follower, is presented to the follower thereby moving the contact 23 to the neutral position.

It will be apparent from the foregoing that by employing two follow-up cams arranged in the manner described, it is possible to mount the insulated contacts of the two switches stationarily. Also the cam surfaces 21 and 2l may be extended through substantially more than a half revolution.

I claim as my invention:

1. In a system for controlling the operation of a reversible power operator to cause an element driven thereby to follow the movements of a control element, two open face cams disposed side by side and mounted for rotation relative to each other about a common axis, said cams being rotatable in unison with said driven element and control element respectively and having peripheral rise surfaces crossing each other, a follower engageable with both of said surfaces, a device for controlling the operation of said power operator and having a part movable back and forth between two limit positions through aneutral position in which said power operator is idle, a member swingable about a. fixed pivot and carrying said movable control part, and a yieldable spring connection between said follower and said member.

2. In a system for controlling the operation of a reversible power operator to cause an element driven thereby to follow the movements of a control element, two cams mounted for rotation Y relative to each other and respectively rotatable in unison with said driven element and control element, said cams having peripheral rise surfaces crossing each other, a follower engageable with both of said surfaces, a device for controlling the operation of said power operator and having a stationary part and a coacting movable part, and a yieldable spring connection between said follower and said movable part.

3. In a system for controlling the operation of a reversible power operator to cause an element driven thereby to follow the movements of a control element, two cams mounted for rotation relative to each other and having oppositely inclined rise surfaces, said cams being rotatable in unison with said driven element and control element respectively, a follower engageable with both of said surfaces, a device for controlling the operation of said power operator and having a part movable back and forth between two limit positions through a neutral position and means providing a connection between said follower and said movable part and operable to hold the part in said neutral position when the corresponding points on said cam surfaces coincide with each other.

4. In a system for controlling the operation of a power operator to cause an element driven thereby to follow the movements of a control element, two cams respectively rotatable in unison with said driven element and control lelement and having surfaces with gradual rises crossing each other, a device for controlling the operation of said power operator, and a follower engageable witlii both of said rises arranged to actuate said dev ce.

5. In a follow-up mechanism, the combination of a pair of cams mounted for rotation relative to each other and having gradual rise surfaces, a movable follower engageable with both of said surfaces, -and an energy control device held in a neutral position when corresponding points on said surfaces are presented to said follower, said device being movable in opposite directions from said neutral position inresponse to turning of the respective cams in opposite directions.

6. In a follow-up mechanism, the combination of a pair of cams mounted for rotation relative to each other and having gradual rise surfaces, a movable follower engageable with both of said surfaces, an energy control device having a neutral position between opposite limit positions, and means providing a yielding connection between said follower and said device for locating the device in said neutral position when the cams are in any one of a multiplicity of positions in which the corresponding points in said surfaces are presented to said follower, said device being moved to one or the other of said limit positions in response to turning of the respective cams out of such position.

7. In 'a system for controlling the operation of a power operator to cause an element driven thereby to follow the movements of a control element, two cams having correspondingly inclined rise surfaces and mounted side by side for movement relative to each other longitudinally of their surfaces, said cams being movable in unison with said driven element and control element respectively, a follower engageable with both of said surfaces, a device for controlling the operation of said power operator, and means providing a. yieldable spring connection for transmitting the motion of said follower to said device.

8. In a follow-up mechanism, the combination of a pair of cams mounted side by side for movement relative to each other, and having oppositely inclined rise surfaces crossing each other, a follower engaging both of said surfaces, and an energy control device actuated by said follower.

9. In a follow-up mechanism, the combination of a power operator having an element driven thereby to follow the movements of a control element, a pair of cams mounted side by side for movement relative to each other and having oppositely inclined rise surfaces, a follower engaging both of said surfaces, and an energy control device actuated by said follower, one of said cams being movable with said control element and the other being operable by said driven element.

JAMES W. DRAKE.

REFERENCES CITED UNITED STATES PATENTS Name Date Davis Sept. 3, 1929 Number 

